Audio problem: When Tango takes his first shot at the tanker at the beginning, the guy in the passenger seat says, "Shit!" However, the way his lips move, that can't possibly be what he's saying.
Continuity mistake: During the brawl in the prison boiler room, Tango hits one of the cons with the hatch of one of the boilers. Tango holds onto the boiler in one shot but not in the next.
Continuity mistake: When you see Conan on the surveillance screen inside the prison, screaming, "Bring them to me!" his hands are at pretty much shoulder level on the bars. But, in the very next shot of him, his hands are much lower on the bars, not even in the shot.
Answer: He was doing a combat reload, where you eject all the rounds, spent or not and fill the revolver with new ones. It guarantees six shots, rather than relying on "indexing" where you count every round fired.
stiiggy
That doesn't make any sense since he hadn't fired a single round and the gun was fully loaded.
It's hard to tell, but it does look like there were at least some empty shells that land on the ground. A revolver isn't going to eject spent shells, so there's no way to say it was fully loaded.
Bishop73